Battery module of parallel electric cell rod bodies

ABSTRACT

An electric cell module is provided, which enables operations of connecting terminals in one direction and which is, as a whole, highly rigid and has excellent resistance to breakage. A pair of rod bodies  3 A and  3 B are arranged parallel to each other to be oriented in opposite polarities. Each rod body contains a plurality of electric cells  1  connected in series through cell connector portions  2 . An electrical connecting structure  4  is formed on one end face of each rod body. The structure connects the rod bodies electrically to each other. A coupling jig  5  is incorporated to surround at least one juxtaposed pair of cell connector portions present at the same longitudinal position in the rod bodies.

TECHNICAL FIELD

The present invention relates to an electric cell module, morespecifically to an electric cell module which is U-shaped as a whole toenable terminal connecting operations in one direction, which is highlyrigid as a module to hardly undergo damage when subjected to externalforces including vibration and also has a high natural frequency toundergo no damage under resonance with external vibrations, and which issuitably used as a power source for driving, for example, an electricvehicle.

BACKGROUND ART

There have recently been discussed use of nickel hydride rechargeablebatteries as power sources for driving various kinds of machine tools,electric motor-assisted bicycles and electric vehicles. In such cases,for example, in an electric vehicle, an output voltage of 100 to 300 Vis necessary.

In order to obtain such output voltage, a plurality of electric cellsare usually connected in series to assemble an electric cell module, andafter a plurality of such electric cell modules are connected in series,the resulting assembly of cell modules is supported by a supportingplate or the like and is as such contained in a container to assume anelectric cell pack structure having a desired output voltage.

An example of the electric cell module is shown in FIG. 1. In thiselectric cell module A, five electric cells 1 are connected in series toassume a rod-shape as a whole. Here, if the rod-shaped module is coveredentirely with a heat-shrinkage tube, it not only attains the primaryobjective of insulation but also can enhance the strength of the entiremodule. Cell connector portions 2 for connecting electric cells 1generally have a structure described below.

The structure will be described based on FIG. 2 showing an explodedcross-sectional view.

First, there are prepared a dish-like connecting piece 2A that is madeof a conductive material and has a stepped structure having alarge-diameter portion and a small diameter portion, and also aring-shaped intervenient piece 2B made of an insulating material. Theupper opening in the large-diameter portion of the connecting piece 2Ais of such a diameter as can permit insertion of a can bottom 1 b of anelectric cell to be connected thereby, whereas a through hole 2 apermitting insertion of a positive terminal 1 a of another electric cellto be connected is defined in the small-diameter portion.

Meanwhile, a through hole 2 b permitting insertion of the small-diameterportion of the connecting piece 2A is formed in the intervenient piece2B.

When electric cells 1 are connected to each other, the intervenientpiece 2B is placed on the upper face of the lower electric cell 1, andthen the connecting piece 2A is placed thereon. The intervenient piece2B is located on an upper rim 1 c of the lower electric cell 1, and thepositive terminal 1 a of that cell 1 penetrates through the throughholes 2 b and 2 a to protrude into the small-diameter portion of theconnecting piece 2A, and simultaneously the bottom face of thesmall-diameter portion is brought into contact with a positive plate 1 don which the positive electrode of the electric cell is formed.

Here, the small-diameter portion is designed to have a depth such thatthe bottom face thereof is brought into contact with the positive plate1 d, when these elements are arranged as described above.

Next, the small-diameter portion of the connecting piece 2A and thepositive plate 1 d of the electric cell on which the positive terminalis formed are subjected to resistance welding to fix the connectingpiece 2A onto the top of the electric cell 1 and simultaneously tosecure electrical connection therebetween.

Subsequently, a can bottom 1 b of another electric cell 1 is put intothe large-diameter portion of the connecting piece 2A to carry out, assuch, resistance welding between the side face of the large-diameterportion of the connecting piece 2A and the can bottom 1 b of the upperelectric cell 1 to immobilize the upper cell 1 in the large-diameterportion of the connecting piece 2A and also to secure electricalconnection between them.

Thus, two electric cells 1 are connected to each other mechanically andelectrically through the connecting piece 2A. Here, the intervenientpiece 2B is incorporated so as to prevent the short-circuitingphenomenon to be caused, for example, when the upper electric cell istilted and as such brought into contact with the lower electric cell bya force like bending is applied to the entire electric cell module.

However, the conventional electric cell module A shown in FIG. 1involves the following problems:

(1) Since the module as a whole assumes an I-shaped rod body and thecell connector portion 2 and each electric cell are connected to eachother by resistance welding to form a point-connection structure, themodule does not have very high strength and yields to external forces,particularly to flexural forces.

Therefore, for example, when a pack structure is to be assembled bycontaining the electric cell module A in a container such as of asynthetic resin, deliberate operations are required so that the modulesare not bent. Meanwhile, troubles can happen that the electric cellmodule A is broken, if some external force is applied to the assembledpack structure.

(2) In this electric cell module A, the rod body composed essentially ofelectric cells connected in series has a positive terminal and anegative terminal at its ends respectively. Thus, when the rod body iscontained in a container to assemble a pack structure, these terminalsare to be connected to other parts in two directions. Further, when oneoperator performs this connecting operations, he or she must move fromone position to another; whereas when two operators perform thisoperation, productivity in module assembly will be lowered.

(3) In addition, when the pack structure having the electric cell moduleA contained in a container is used as a drive power source of anelectric vehicle and the like, the structure resonates with vibration ofthe vehicle itself or with external vibrations, due to the low naturalfrequency of the electric cell module A, to induce great vibrations,causing occasionally damage of the electric cell module A and othertroubles.

While various kinds of automotive parts, taken for example, aresubjected to tests according to the vibration testing methods forautomobile parts of the Japanese Industrial Standards (JIS D1601) in thepreset frequency range of 5 to 100 Hz. In order to solve the problemsdescribed above and in view of this circumstance, it is essential forelectric cell modules to have a natural frequency of higher than 100 Hzso as to avoid the above frequency range.

It is an object of the present invention to provide an electric cellmodule of a novel structure, which has overcome the problems inherent inthe conventional electric cell module A and which is, as a whole, highlyrigid, enables terminal connecting operations in one direction and has ahigh natural frequency to be free from damage by resonance withvibrations applied thereto.

DISCLOSURE OF THE INVENTION

In order to attain the intended objective as described above, thepresent invention provides an electric cell module containing a pair ofrod bodies arranged parallel to each other to be oriented in oppositepolarities, each rod body containing a plurality of electric cellsconnected in series through cell connector portions; an electricalconnecting structure formed on one end face of each rod body, thestructure connecting the rod bodies electrically to each other; and ajig for coupling the rod bodies, the jig surrounding at least onejuxtaposed pair of cell connector portions present at the samelongitudinal position in the rod bodies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in plan view an example of conventional electric cellmodule;

FIG. 2 is an exploded cross-sectional view of a cell connector;

FIG. 3 is a perspective view of an electric cell module B1 according toone embodiment of the present invention;

FIG. 4 is a plan view of the electric cell module B1;

FIG. 5 shows in exploded cross-sectional view an electrical connectingstructure in the electric cell module B1;

FIG. 6 shows in perspective view an example of coupling piece 5A;

FIG. 7 shows in front view another example of coupling piece 5B; and

FIG. 8 is a perspective view of an electric cell module B2 according toanother embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Electric cell modules according to the present invention will bedescribed below referring to the drawings. FIG. 3 is a perspective viewof an electric cell module B1 according to one embodiment of the presentinvention; and FIG. 4 is a plan view thereof.

This electric cell module B1 uses two rod bodies 3A and 3B each havingfive electric cells 1 connected in series. In this module B1, while thestructure of the cell connector portions 2 for connecting electric cells1 in each rod body is not particularly limited, it should be understoodhere that they have the connecting structure as shown in FIG. 2.

The rod bodies 3A and 3B are arranged parallel to each other with a verysmall clearance being secured crosswise therebetween and are oriented inopposite polarities. Thus, the cell connector portions 2 in one rod bodyand those in the other body are located substantially at the samelongitudinal positions, respectively.

An electrical connecting structure to be described later is formed atone end of each rod body to secure serial electrical connection betweenthe rod body 3A and the rod body 3B, and the thus connected rod bodiesas a whole assume a U-shape.

In at least one juxtaposed pair of cell connector portions 2 (two pairsin FIG. 2) in the rod bodies 3A and 3B, a coupling piece 5 (to bedescribed later) is incorporated to surround them, as a measure forreinforcing the rod bodies 3A and 3B.

Therefore, in the case of the electric cell module B1, a terminal(assuming that it is a positive terminal) 3 a of the rod body 3A and aterminal (negative terminal) 3 b of the rod body 3B are oriented in thesame direction, and this enables terminal connecting operations in onedirection.

Here, a method of assembling an electrical connecting structure 4 givenhere as an example will be explained referring to FIG. 5.

In FIG. 5, a dish-like jig 4A made of a conductive material is placed onthe positive end of an electric cell 1 in the rod body 3B to be incontact with a positive terminal 1 a of the cell 1 and with a positiveplate 1 d on which the terminal 1 a is formed. This dish-like jig 4A hasat the center a boss 4 a having the same outline as that of the positiveterminal 1 a of the cell 1.

The dish-like jig 4A has an outside diameter such that a very smallclearance is formed between the inner wall surface of an upper rim 1 cof the electric cell 1 and the jig 4A, when the jig A is placed on thepositive end of the cell 1.

Then, the positive terminal 1 a, the positive plate 1 d and the jig 4Aare subjected to resistance welding to fix the jig 4A onto the positiveend of the electric cell 1.

Next, an annular jig 4B, which is made of an insulating material and hasa diameter slightly larger than the outside diameter of the jig 4A, awall thickness equal to the width of the clearance and a collar 4 bextending outward from the barrel, is fitted in the clearance. Thus, thejig 4B is supported at the collar 4 b by the upper rim 1 c of theelectric cell, whereas the barrel of the jig 4B is located in theclearance between the jig 4A and the upper rim 1 c. This structureprevents short-circuiting from occurring between the electric cells 1.

Meanwhile, a bus-bar structure 4C made of a conductive material such ascopper is prepared. In this bus-bar structure 4C, one end portion 4 cthereof has a diameter substantially equal to the inside diameter of thejig 4A and has at the center a recess 4 d of substantially the sameoutline as the boss 4 a of the jig 4A. The other end portion 4 e has adish-shaped body 4 f fixed thereto by means of resistance welding. Thedish-shaped body 4 f has a diameter substantially equal to that of thecan bottom 1 b of the electric cell 1 in the rod body 3A.

Then, the end portion 4 c of the bus-bar structure 4C is fitted in thejig 4A, whereas the can bottom 1 b of the electric cell 1 in the rodbody 3A is fitted in the dish-shaped body 4 f, thus forming anelectrical connecting structure 4 for connecting the rod body 3A and therod body 3B electrically to each other.

It should be noted here that the electrical connecting structure in theelectric cell module according to the present invention is not to belimited to the above embodiment, but other embodiments can be employed.For example, the bus-bar structure is bridged between the terminals 3 aand 3 b of the rod bodies and is fastened to the terminals 3 a and 3 busing bolts or other means. Meanwhile, other conductive materialsemployable here include metallic materials based on copper includingbrass, aluminum alloys and nickel-plated iron.

Next, the coupling piece 5 to be incorporated between two rod bodieswill be described.

FIG. 6 shows an example of coupling piece 5A. The coupling piece 5A is ablock having a predetermined thickness and a curved face one each side.The block contains a pair of through holes 5 a and 5 b defined at apredetermined interval.

Here, the through holes 4 a and 5 b have diameters substantially equalto the outside diameters of the rod bodies 3A and 3B, and the portion 5c between the through holes 5 a and 5 b is as wide as the clearancebetween the rod body 3A and the rod body 3B and serves as a spacer forholding the rod bodies with a certain clearance.

Referring to assembling of the electric cell module B1 shown in FIG. 3,the rod bodies 3A and 3B are inserted to the through holes 5 a and 5 bof the coupling piece 5A, respectively. The coupling piece 5A is thenlocated on a desired juxtaposed pair of cell connector portions 2.

The pair of cell connector portions 2 are surrounded by the walls of thethrough holes 5 a and 5 b, while the coupling piece 5A is incorporatedbetween the rod body 3A and the rod body 3B to hold them with apredetermined clearance secured therebetween. Even if a flexural forceis applied to the rod bodies, the coupling piece 5A controls bending ofthe rod bodies to effectively prevent breakage of the module at theelectrical connecting structure 4 when functioned as a fulcrum.

The coupling piece 5A preferably has a thickness equal to or slightlygreater than the width of the cell connector portion 2. The walls of thethrough holes 5 a and 5 b in the coupling piece 5A surround the cellconnector portions 2 completely to protect them, so that deformationincluding, for example, dislocation and bending between two electriccells connected by the cell connector portion 2 can more effectively becontrolled.

Further, the coupling piece 5A desirably has a flat upper face 5 e and aflat lower face 5 e. In the case of an electric cell module B1 assembledusing such coupling pieces 5A, a plurality of cell modules can bedirectly stacked successively by bringing such flat faces into contactwith each other. More specifically, the supporting plate (not shown)serving also as a cell module holder having been necessary in the caseof the packed structure where the conventional electric cell modules arecontained in a synthetic resin container or the like, can be omitted,facilitating assembling of the pack structure.

Meanwhile, if recesses and protrusions which are engageable with eachother are formed on the upper face and the lower face respectively toconstitute an engagement structure, it ensures not only stacking ofelectric cell modules but also realization of the structure forsupporting them.

FIG. 7 shows another example of coupling piece 5B.

This coupling piece 5B has a double-split structure composed of an upperhalf 5B₁, and a lower half 5B₂. These halves 5B₁ and 5B₂ each containtwo semicircular curved surfaces which form, when combined, two circularholes having a diameter substantially equal to those of the rod bodies3A and 3B. A screw hole 5 f or the like is defined in the upper half5B₁, as well as, in the lower half 5B₂ in alignment with each other, sothat these halves can be combined and fastened together by screwing ascrew into these screw holes.

When the coupling piece 5B is to be incorporated between the rod body 3Aand the rod body 3B, the upper half 5B₁ and the lower half 5B₂ arelocated to oppose each other across a desired juxtaposed pair of cellconnector portions, as shown in FIG. 7, and are combined with eachother, followed by fastening by screwing a screw into the screw holes 5f.

The rod body 3A and the rod body 3B are surrounded by the walls ofcircular through holes defined by the semicircular faces of the upperhalf and the lower half, and coupling pieces 5B each composed of theupper half and the lower half are incorporated between the rod body 3Aand the rod body 3B to give an assembled electric cell module B1 asshown in FIG. 3.

The coupling piece 5B having such a structure can suitably be used evenwhen the diameters of the rod bodies are different from the borediameters of the through holes. Because the coupling piece 5B can beincorporated between a pair of rod bodies to surround the desiredjuxtaposed pair of cell connector portions securely by combining thehalves and adjusting the degree of fastening them with a screw. Forexample, even in a case of rod bodies each covered with a heat-shrinkagetube, this coupling piece 5B can be incorporated readily between suchrod bodies.

Further, the means of fixing the rod bodies using this coupling piece 5Binclude, in addition to the screw to be screwed into the center of thecoupling piece 5B, one where the upper half 5B₁ and the lower half 5B₂are fastened to each other at each side end; e.g., a hinge or the likeis fixed to one side end of the upper half 5B₁, and to that of the lowerhalf 5B₁, while a hook or the like is attached to the other side end ofthe upper half 5B₁ or the lower half 5B₂ and the hook is hooked onto therest of them so as to fasten them together; or a hook is attached toeach side end of the upper half 5B₁ or the lower half 5B₂ and the hooksare hooked onto the rest of them so as to fasten them together.

It is preferred to apply an elastic body such as a rubber to the wallsof the through holes 5 a and 5 b in the coupling piece 5A or to thesemicircular curved faces of the upper half 5B₁ and the lower half 5B₁,in the coupling piece 5B. That is, if an elastic body is applied to suchfaces of the coupling piece surrounding the rod bodies, the elastic bodysecurely blocks the clearance present between the coupling piece and therod bodies to prevent backlash from occurring between them afterincorporation of the coupling piece.

FIG. 8 shows an electric cell module B2 according to another embodimentof the present invention. In the case of this electric cell module B2,three electric cells 1 are connected in series to form a rod body 3A(3B). The thus obtained rod bodies 3A and 3B are connected to each otherwith the electrical connecting structure 4 described above, and couplingpieces 5 are attached to all of the cell connector portions (two pairsof cell connector portions in this case) to surround them, respectively.

In this electric cell module B2, since the cell connectors are allimmobilized with the coupling pieces 5 respectively, the module B2 as awhole is highly rigid compared with the module B1 and enjoys highreliability in terms of resistance to breakage.

As described above, the electric cell module according to the presentinvention assumes a U-shape having coupling pieces incorporated betweena pair of rod bodies to enable terminal connecting operations in onedirection. In addition, since the coupling pieces securely hold a pairof rod bodies, the electric cell module has a structure that controlsdamage by resonance with external vibrations.

EXAMPLE

A pair of rod bodies 3A and 3B each having a total length of 270 mm werefabricated using five electric cells having a diameter of 32 mm and aheight of 50 mm for each rod body. An electric cell module B1 as shownin FIG. 3 was assembled using these rod bodies. Here a clearance of 41mm was secured between the rod bodies 3A and 3B.

Natural frequency of the electric cell module B1 was measured in thefollowing manner.

The electric cell module B1 was bound with a string at the center of theelectrical connecting structure and was suspended with it. Anacceleration sensor was attached to the distal electric cell in one ofthe rod bodies. In the state where the module B1 is supported to havefree ends, the module B1 was hammered to measure the natural frequencywith the acceleration sensor.

As a comparative example, natural frequency of the conventional electriccell module A shown in FIG. 1 was measured likewise.

The electric cell module B1 had a natural frequency of 120 Hz; while theelectric cell module A had a natural frequency of 85 Hz.

As is clear from these results, the electric cell module B1 of thepresent invention (example) had a natural frequency of higher than 100Hz, although the conventional electric cell module A (comparativeexample) had a natural frequency of 85 Hz. Therefore, the electric cellmodule B1 of the present invention undergoes no damage, since itresonates neither with the vibration of the electric vehicle itself norwith external vibrations to undergo no sympathetic vibration.

INDUSTRIAL APPLICABILITY

The electric cell module according to the present invention as a wholeassumes a U-shape to enable terminal connecting operations in onedirection, and enjoys excellent handleability in actual uses. Since theelectric cell module is provided with a pair of rod bodies, eachcontaining a plurality of electric cells, and coupling piecesincorporated between the rod bodies to surround them, the cell connectorportions are reinforced by the coupling pieces, so that the module showsexcellent resistance to flexural forces and is as a whole highly rigid.Thus, if the electric cell module is used actually as a power source fordriving, for example, an electric vehicle or a machine tool, it does notresonate with vibrations of the vehicle or the tool to hardly undergotroubles including breakage.

What is claimed is:
 1. An electric cell module, comprising: a pair ofrod bodies arranged parallel to each other to be oriented in oppositepolarities, each rod body containing a plurality of electric cellsconnected in series through cell connector portions; an electricalconnecting structure formed on one end face of each rod body, thestructure connecting the rod bodies electrically to each other; and ajig for coupling the rod bodies, the jig surrounding at least onejuxtaposed pair of cell connector portions present at the samelongitudinal position in the rod bodies.
 2. The electric cell moduleaccording to claim 1, wherein the jig for coupling the rod bodies has adouble-split structure.
 3. The electric cell module according to claim1, wherein the jig for coupling the rod bodies has on the facessurrounding the cell connector portions an elastic body.
 4. The electriccell module according to claim 1, wherein the electrical connectingstructure is made of copper, a copper-based metal, an aluminum alloy ornickel-plated iron.
 5. The electric cell module according to claim 2,wherein the jig for coupling the rod bodies has on the faces surroundingthe cell connector portions an elastic body.